(a) Field of the Invention
The present invention relates to a system for treating natural gas from a gas source to make it suitable for safe transport in high tensile strength steel pressure vessels at pressures in excess of 2000 psi and to unload the natural gas at a remote user facility in a system capable of feeding a constant supply of pressurized gas to the user.
(b) Description of Prior Art
The transportation of natural gas by transport vehicle has been known for many years in countries such as Italy and France. Also, it has long been known in Italy, for example, to utilize compressed natural gas to operate vehicles. Thus, natural gas is taken from a gas well and pressurized to a high pressure (in the order of 250 bars) and transported in vessels mounted on a vehicle whereby to distribute the pressurized gas to small gas distribution stations where the gas is unloaded and stored in high pressure containers to later be discharged in the pressure vessels of vehicles. Such a system is described in a publication entitled "Manuel pour le Transport et la Distribution du Gaz" published in 1968 by the Societe du Journal des Usines a Gaz, 62, rue de Courcelles, Paris (VIII), which publication is put out by the Technical Association of the Gas Industry of France.
Canadian Pat. No. 1,073,399 issued Mar. 11, 1980 describes a method and system for transporting well known principles as described in the above-mentioned French publication and was developed primarily for the collection and transport of gas from gas wells where it is uneconomical to build a feeder pipe line and particularly where the wells were low-producing, isolated or located in remote places. The advent of high energy costs has brought about the feasibility of transporting compressed natural gas by vehicle. However, it has been found that in order to safely handle natural gas at the loading station (where the gas wells are located) during transportation by road vehicles, and at a discharge station, various problems were required to be solved. A major problem in handling natural gas is the formation of hydrates in the gas which results when the gas undergoes cooling, such as in underground pipe lines. A hydrate is a clathrate chemical combination of water in the liquid phase and light hydrocarbon molecules in the form of a crystal. The necessary water for hydrate production is present in all hydrocarbon reservoirs and may reach the surfaces either as produced or condensed water. Produced water flows in the reservoir and enters the well bore in liquid form. Condensed water is in the vapor phase at reservoir conditions that condenses out at the reduced temperatures achieved through expansion of the gas to low pressure and/or heat exchange at the surface of the well. The condensation of the water into the liquid form presents a problem to the vessels of transport vehicles since these vessels are constructed of high tensile strength steel which is susceptible to corrosion and subsequent failure.
When a gas loading facility is located in the vicinity of two or more gas wells, it is also necessary to ensure the safe delivery of the gas from the gas well to the loading facility, particularly when one of the wells is connected to the facility by approximately a one-mile pipe line. Another disadvantage which arises when transporting natural gas by road vehicles is that a constant supply of gas at an unloading station must be ensured, particularly when that unloading station is feeding a user which cannot shut-down. Due to inclement weather conditions, vehicle break-downs or slow-downs frequently occur and there is thus a need to provide an unloading station having a capability that will ensure continuous supply of gas.